The present invention relates to a method of controlling image formation in an image generating apparatus, and more particularly to a method of controlling image formation in an image generating apparatus by controlling image forming conditions in order to keep, at preset levels, the potentials of a reference black pattern latent image and a reference white pattern latent image, respectively, which are formed on a latent image carrier.
Latent image carriers such as photosensitive bodies or various chargers and lamps are deteriorated due to aging and varying environmental conditions, and cannot remain stable over a long period of time. Therefore, various image forming conditions such as charging conditions of chargers, lamp voltages, and bias voltages for developing images are appropriately corrected and controlled. According to one procedure for such control, electrostatic latent images corresponding to black and white patterns, respectively, of a reference density are formed on a latent image carrier, and the above image forming conditions are controlled such that the potentials V.sub.D, V.sub.L of the respective latent images will be kept at appropriate preset levels.
According to the conventional method of controlling the image forming conditions, however, the image forming conditions are controlled independently of each other. Therefore, while a certain image forming condition being controlled may be set to a target value, the other image forming conditions are affected thereby to fail to achieve a proper potential upon image development, resulting in the problems of unstable image quality and excessive control over a certain image forming condition. Another drawback is that an interface interconnecting individual units fails to provide adequate matching between the units, and hence images cannot well be formed unless each unit has increased reliability.
With the individual image forming conditions being independently controlled, images cannot be reproduced with high fidelity as the units are related to each other. For example, when a photosensitive body is deteriorated by charging fatigue, its sensitivity may be lowered and optical fatigue may also be produced. Therefore, if the charging fatigue is corrected by a charging charger, the sensitivity of the photosensitive drum may be lowered. If the charging fatigue is corrected by an image developing bias, an appropriate potential for developing images may be obtained, but stains or scumming may develop which makes it difficult to keep a good image quality.
As the latent image carrier is deteriorated, more and more charges remain on the latent image carrier. When such a residual potential exceeds the preset level of the potential V.sub.L of the electrostatic latent image corresponding to the reference white pattern, it becomes impossible to keep the potential V.sub.L to the preset level. These problems can no longer by solved by the conventional control system.